I will stay in Mammoth (I coludn't find a Hotel with vacancy in Yosemit....) and have no idea how is the best way to go to Yosemit.I will have a rented car, but google earth told me that it takes almos t 2 and 1/2 hours....There is any kind of bus that I can take in Mammoth to go and back?

I will have 3 nights in Mammoth. If I take just one full day in Yosemit is ok, or is best go back a second day?

It will still takes 2 1/4 hours bus or rented car. There are closer places to Yosemite Valley than Mammoth Lakes. I suggest looking at lodging at El Portal, Mariposa, and Oakhurst. They are 30, 70, and 90 minutes from Yosemite Valley.http://www.yosemite.ca.us/lodging.html

If you stay in Mammoth Lakes, you can visit Tuolumne Meadows in the park. It's a beautiful high-altitude meadow with rock formations.

Don't miss out on all the valley has to offer. One day may not be enough. If you like hiking the half dome hike will take you all day, but well worth it. The Vernal falls hike is incredible right now. Most people don't continue up to Neveda falls from Vernal but that is also worth the time. Take a chair with you to Mirror lake and sit on the beach and have a beer for a while. Most people just walk up to it and look then leave. It's great to sit there and look up at half dome. Upper Yosemite falls is a great hike too but it's also nice to just look at lower Yosemite falls from the bridge. Happy Isles is also overlooked. It's right next to the Vernal start and most people skip it. Hike back about 300 yards past the end of the trail and find your own spot and enjoy the view. Finishing your afternoon in Curry Village with some pizza and beer is the best!

Renting a car and staying in Mammoth is not a bad deal. The drive you'll have is beautiful. Get up early and go. Don't miss out on all that Mammoth has to offer. Renting a moutain bike and doing the trails is fun. Sitting in the sun at the Yodler is a good way to finish the day. Angels restaruant on Main and Sierra has great good and good beer. Hanging out in the village is also a fun afternoon. The Rainbow falls hike in Mammoth is very dusty and the clay can bother some people. The end of the hike is a beautiful waterfall. Lake Mary in Mammoth is also killer to rent a boat and fish on.

Remember to leave early...I'm thinking by 6:30 at the latest. The parking at Curry fills up fast...by 9:30 that lot may be full. The Trailhead parking just past there is also good to look at for parking. As a general rule, as I pass the Sentinel bridge and I see cars already parking on the left next to the meadow I grab a spot there, no need to look in the Curry parking lot.

There is alot of water right now. 3 people just died at Vernal so be careful. I swim in the Merced every year and also at the top of Vernal in the Emerald pool. I had to really be careful this season.